Centrifugal speed-limit device.



W. H. FOOT.

CENTRIFUGAL SPEED LIMIT DEVICE.

APPLICATION FILED FEB. 1, 1912.

1 231 ,5" v Patented July 3, 1917.

WITNESSES:

WMTE STATE PATENT QFFTGEQ WILLIAM H. FOOT, F, WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURINGCOMPANY A CORPORATION OF PENNSYLVANIA."

CENTRIFUGAL' SPEED' -LIIVIIT DEVICE.

Specification of Letters Patent.

Patented July-3, 19317.

Application-filed. February l, 1912." Seria1 No.67 l,8()3.

To all whom-it may camera:

Be it known that I, ;W1LL-1A1\I H F001, a subject of the King ofsGreat-Brltain iandra resident of lVilkinsburg, in the county of 5 Alleghenyand State ofPenn'sylvama,have and useful Improvement in,

invented'a new J Centrifugal Speed-Limit DBVICGS, of which the following is a specificatlon:

My invention relatesto centrifugal speeds: limit devices and it has SPGCIEUl l'EfBI'GII-CStO chines, for the purpose of automaticallypre-i venting excessive speeds; a,

The object :of my invention is'atov-provide' a device of the above-indicatedcharacter that: shall 3 be simple, inexpensive and idll l'l ble in construction and effective and reliable in operation, and be particularly: adapted-to effect a positive operation of: a switching device with'whichlitis associated:

In the prior. art, centrifugal speed-limit devices of thisgeneral class i'ha-verbeenemployed for the purpose hereinbefore fied, but, usuallyythe automatic tripping portions of the [devices have ibeen con-= structed'and operated in: substantially the manner of engine shaft governors that: are adapted for specd-regulationl and in which the positions of the centrifuga'lly-:actuated arms are dependent upon :variationsnin speeds Furthermore, the striking engage ments of the arms and the pawls or latches of *the' switching devices have been'effected at the ends of said arms. =Thus,f-.the centrifugally-actuatedt arms 1 usually delivered a series of rapid "and:-light'rblows =to the switching members prior to their final re lease, and the tripping actionswere alsounreliable, by reason of the factithatth'e 'e'ngagement of the centrifugally-actua-ted arms and "the switch "members were effected at points which requiredthe minimumlamount ofresistance to overcome the torque due to, centrifugal force. According .to my presentrinventiom'l iprovide' a speed limitrdeviee :WhlOll isuso con structed as to ELVOlClth objeetions hereinbe fore mentioned and to secure reliability-guru formity. and :positivenesswin its operation. The tripping portioniofzthe device embodied in my invention;comprises a pivotally mounted member which is provided with a weight ed end portion and atstrilaing' nr engaging specie portion located substantially as the center of percussionef the member:

F urthermore; an extension of said-1nember projectsbeyond-its pivotal support and is engaged by a-spring which acts in opposition to the centrifugal force exerted upon the weighted portionof the arm until a predetermined speed is reached when the spring acts with decreasing effect. By reason of this construction, the weightedarm is moved quickly-from its initial inner position to its outer position, and-the engagement of the striking portion of-the pivotcdarm: and the coiiperating switch member is efiected at approximately the center of percussion of said arm, so that-the switching device is positively'actuated by a single blow.

' My invention may-best beunderstood by reference to'the accompanying drawing, in

which Figure l is anend view, partially in section, of a speed-limit device constructed in aceordance'witlr my invention; Fig. 2 is a view, in side elevation, iofthe tripping portion of the deviceshown in Fig. 1, and Fig.8 is a sectional view, taken along the Ii'ne HI I II of Fig. 1, showing the arrangement ofthe cooperating contact members of the switching portion 'ofthe device when the switch is closed;

Referring to1the drawinggthe apparatus shown comprises, in general, a tripping device 'l andaaswitching device'2, said tripping-device being fixed to a rotatable shaft 3, and:comprising a main-body member 4, and a pivotally mounted spring controlled member- 5, while the switching device 2 is suitably mounted in cooperative relationship to the tripping device 1, and comprises acontainingbox or casing 7, a switch member S, a spring 9 and stationary contact terminals 10.

The main body member 4 is of cylindrical formand 'issecuredto the shaft- 3 and provided with a projecting peripheral flange 11, havingai'i openinglQ therein to permit the outward movement of the arm 5, as will he hereinafter'set forth. The member 5 is pivotally mounted upon a pin 13 and is provided, at its free end, with a Weighted portion l la while sin-extension member 15 profleetsslightly beyond its pivotal support. Furthermore, an engaging or striking member 16 forms anintegral part of the ,arm 5 percussion. of said arm;

The extension 15 is provided with a projecting portion 17, which serves as a stop to engage the peripheral flange 11 and prevent the weighted portion 11 of the arm 5 from engaging the shaft 3. The extension. 15 is bifurcated and one end of a guide member 18 is pivotally connected between the arms 19 thereof. The other end of said guide member projects loosely through a hollow plug member 20 which is screwed into an opening 21 that is provided in a lug 22- which constitutes a part of the main body member 4. Surrounding the guide member 18 is a helical spring 23 which engages the extension 15 and the inner end of the plug 20, said spring serving to oppose the outward movement of the arm 5. The plug 20 is provided with a slot 21 into which a suitable implement (not shown) may be inserted, for the purpose of adjusting the compression of the spring 18, whereby the tripping device may be set to operate at any predetermined desired speed, as will be readily understood.

The box or casing 7 is suitably secured to a lug 25 which may form a part of a bearing or pedestal member 26 by means of which the shaft 3 is supported in the usual manner, and the switch member 8 is pivotally mounted on a shaft 27 that is carried by a bracket member 28, forming a part of the casing 7. The upper portion of the switch member 8 constitutes a dog 29 and is.

disposed in the path of the striking mem ber 16 when the arm 5 is in its outer position. The lower portion 30 is provided with an insulating block 31 to which is secured a bridging movable contact member 32 that is adapted to cotiperate with a plurality of stationary contact terminals 10 which are suitably secured in position upon an insulating block 34, the latter being attached to the casing 7 The contact terminals 10 are respectively connected to a plurality of conductors 35.

Inasmuch as the coeperating stationary and movable contact members 10 and 32 form no part of my present invention, eX-' cept as they constitute useful elements in an operative combination, no detailed description of the same is deemed necessary, it being "understood that contact members of any suitable construction may be employed.

The spring 9 is connected between the upper end of the dog 29 and the outer end of a supporting bracket 36 and is so located, with respect to the switch member 8, that said switch member is normally maintained in approximately its dead center position, although actually slightly overset, as clearly shown in Fig. 1. A screw 37 projects through the casing 7 to engage the lower end 30 of the switch member 8 and is adjustable in order to determine the set position of the switching device.

Assuming the shaft 3, to which the tripping device 1 is secured, to be rotating at a constantly increasing speed and that the various parts of the apparatus occupy the positions shown in full lines in Fig. 1, the operation of the device is as follows:

Below the critical speed for which the device is adjusted, the spring 23 acts upon the extension member 15 in opposition to the action of the centrifugal force produced by the rotation of the arm 5 to maintain said arm in its initial inner position. l/Vhen such predetermined speed is attained that the torque, due to the centrifugal force on the arm 5, predominates over the torque produced by the spring 23, the arm 5 is suddenly and positively thrown to its full outer position, indicated in dotted lines. No intermediate position can be maintained for the reason that when-the arm 5 begins to move outwardly, the torque about the piv otal support 13, due to centrifugal force, increases, while that due to the spring 23 decreases as the axis of the spring more nearly parallels a line drawn between the fixed points 13 and 20, so that the resultantforce acting on the arm 5 is constantly increasing, thereby causing the arm 5 to be thrown to its full outer position and preventing any intermediate positions.

When the arm 5 is in its outer position, the striking member 16 is brought into the path of the dog 29 and an engagement between said members 16 effected. Inasmuch as the striking member 16 is located at approximately the center of percussion of the arm 5, a positive and effective blow. is delivered to the dog 29, thereby forcing the switch member 8 beyond its dead center position, after which it is actuated in a clockwise direction with a quick movement by means of the spring 9, to effect a rapid and positive closure of the co'ciperating switch members 32 and 10.7 o f Obviously, it is not essential that the co operating switch members 32 and 10 be closed through the agency ofthe automatic tripping device, as, under certain conditions, it may be expedient to arrange the apparatus in such manner as to efiect the separation of said switch members.

By a series of experimentaltests, I have found that the speed-limit device constituting my invention may be accurately adjusted to any desired speed to operate with reliability, uniformity and positiveness, and I have further determined that when the speed decreases to a predetermined value,

the arm 5 is moved back into its initial poafter the same has been actuated by the trip-. J

device 1 in the manner just described, it is only necessary to forcethe switch memher 8 into its normal set position, which may be done by the operator without removing the cover (not shown) of the casing 7 Although I have shown and described my invention as embodying specific structural details and arrangement and location of parts, it will be understood that many modifications may be el'fected therein without departing from the spirit and scope of my invention, and I desire that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. The combination with a rotatable shaft, of a centrifugal operating device carried thereby comprising a base plate provided with an annular flange having a peripheral opening, a weighted arm pivotally mounted on said base plate within said flange, a striking portion integral with said arm and located adjacent to its pivotal support and to said peripheral opening, the said striking portion being adapted to move outward through said opening and to project beyond the outer periphery of said flange, under the influence of centrifugal force.

2. The combination with a rotatable shaft, of a centrifugal operating device carried thereby comprising a base plate provided with an annular flange having a peripheral opening, a weighted arm pivotally mounted on said base plate within said flange, a

striking portion integral With said arm and located at substantially the center of percussion of said arm and adjacent to said peripheral opening, the said striking portion being adapted to move outward through said opening and to project beyond the outer periphery of said flange, under the influence of centrifugal force.

3. A centrifugal device comprising a rotatable member, a pivotally mounted arm associated therewith and having a weighted portion at its free end, a bifurcated extension projecting beyond the pivotal support of said arm, a guide member pivotally connected between the arms of said extension and projecting loosely into an apertured plug member threaded into a portion of said rotatable member and a spring surrounding said guide member and engaging said extension and said plug to oppose the action of centrifugal force on said arm, the tension of said spring being determined by the position of said threaded plug member.

In testimony whereof, I have hereunto subscribed my name this 17th day of Jan, 1912.

WILLIAM H. FOOT.

Witnesses EDWIN DENHAM, B. B. HINES.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, I). G. 

